PETpla.net Insider 11 / 2020

MATERIALS / RECYCLING PETplanet Insider Vol. 21 No. 11/20 www.petpla.net 14 NGR’s LSP technology has proven itself worldwide Rapid IV build-up Austrian company Next Generation Recyclingmaschinen GmbH (NGR) has been implementing sustainable recycling systems for PET since 2014. The core of the technology is polycondensation in the liquid phase along with highly efficient decontamination, rapid IV build-up and stabilisation of the IV value. In contrast to conventional systems, such as solid state polycondensation (SSP), NGR uses P:React liquid state polycondensation (LSP), which can process up to 3,000kg/h. The process utilises PET’s tendency to rapidly condense in the melt phase, so that the IV value increases quickly and in line with requirements. The process begins with the PET scrap being melted in a stand- ard extruder, such as NGR’s own P:Gran. From there it is delivered to the P:React reactor vessel, where the melt is purified and decontami- nated under high vacuum with a controlled residence time. Different modular filtration technologies are used according to the degree of par- ticle contamination. In the reactor vertical section the melt is divided into numerous individual strands, which then drop through the high-level vacuum, with an extremely high surface area expo- sure. The increase in surface area allows the contaminants to be quickly removed. The melt collects in the hori- zontal section, where it remains for up to 30 minutes. A slow rotating augur further creates surface area exposure to the vacuum, where polycondensa- tion is completed. An example concept of a complete solution: Fig. 1 LSP schematic diagram NGR’s high-level vacuum removes nearly 100% of all critical impurities found in PET waste. The filtered-out substances are collected in a redun- dant filter system, where they can be cleaned out without interrupting operations. The LSP’s decontamination perfor- mance makes it open to a wider range of applications than other processes. The P:React has been successfully used in the film and fibre sector for several years already and NGR has installed several operating systems across the world for bottle-to-bottle recycling. More systems continue to being commissioned, as major bever- age brand owners test, veryify and approve the LSP process for recycling post-consumer waste. LSP has also received food certifications such as FDA and EFSA. The main qualification that rPET must meet to achieve food-grade status is the extensive removal of all contaminants in a continuous process. The graph in fig. 2 shows that the decontamination levels achieved by the LSP exceed FDA requirements in all areas. This ensures that both post-con- sumer and post-industrial PET waste is transformed into valuable rPET, with consistent IV value and consistent food safety, in the shortest possible time. The importance of quality and IV value of the input material is mini- mised as the LSP can achieve up to 30% IV increase. The entire process takes only minutes, rather than the hours required by conventional SSP methods. Fig. 2 Decontamination performance, certified for 100% food contact Consistent output IV and melt quality is achieved with two control parameters: 1) Vacuum pressure and 2) Residence time in the reac- tor. LSP production is a continu- ous (rather than batch) process and requires no process aids, such as nitrogen gas. Taking advantage of the energy efficiency associated with such a short residence time, while avoiding the high costs of nitrogen supply, helps to achieve very low overall operating costs. Increased demand and the sensi- tive price structure of input materials, such as bottle flakes, require that continuous process, along with a high flexibility in the technology. The SSP process is generally used to pro- duce batches whose quality depends essentially on the input material. Analyses have shown that, within any given batch of post-consumer bottle flake, there is considerable variation in IV level and degree of impurity. RECYCLING